Method and Control Unit for Detecting the Closed State of a Clutch in a Drive Train of a Motor Vehicle

1 . A method for assessing a closed state of a clutch in a drive train of a motor vehicle, a driver using the clutch for controlling a frictional connection between an internal combustion engine and a change speed transmission of the motor vehicle, which comprises the steps of:

determining a difference in a rotational speed occurring across the clutch; and

carrying out an assessment of the closed state in dependence on a signal of a sensor detecting activation of the clutch and in dependence on the difference in the rotational speed.

2 . The method according to claim 1 , which further comprises generating a further signal characterizing a closed clutch if the sensor detects no activation of the clutch.

3 . The method according to claim 1 , which further comprises generating a further signal characterizing a closed clutch if the sensor detects activation of the clutch lasting for longer than a predetermined minimum period and an absolute value of the difference in the rotational speed drops below a predetermined threshold value.

4 . The method according to claim 3 , which further comprises generating another signal characterizing an open clutch if the sensor detects activation of the clutch and a predetermined delay time has passed since detection.

5 . The method according to claim 4 , which further comprises setting the predetermined minimum period to be longer than the predetermined delay time.

6 . The method according to claim 1 , which further comprises generating a further signal characterizing an open clutch if the difference in the rotational speed across the clutch exceeds a predetermined threshold value.

7 . The method according to claim 1 , which further comprises:

sensing a rotational speed of the internal combustion engine as a first rotational speed;

sensing a rotational speed of a transmission input shaft as a second rotational speed; and

determining the difference in the rotational speed across the clutch as a difference between the first rotational speed and the second rotational speed.

8 . The method according to claim 1 , which further comprises:

sensing a rotational speed of the internal combustion engine as a first rotational speed;

sensing a further rotational speed in the drive train at an output end of the change speed transmission;

determining a rotational speed of the transmission input shaft as a second rotational speed from the further rotational speed and a transmission ratio; and

determining the difference in the rotational speed across the clutch from a difference between the first rotational speed and the second rotational speed.

9 . A control unit for assessing a closed state of a clutch in a drive train of a motor vehicle, with the clutch a driver controls a frictional connection between an internal combustion engine and a change speed transmission of the motor vehicle, the control unit comprising:

a controller programmed to:

determine a difference in a rotational speed occurring across the clutch; and

assess the closed state of the clutch in dependence on a signal of a sensor detecting activation of the clutch and in dependence on the difference in the rotational speed.

10 . The control unit according to claim 9 , wherein said controller is further programmed to generate a further signal characterizing a closed clutch if the sensor detects no activation of the clutch.

11 . The control unit according to claim 9 , wherein said controller is further programmed to generate a further signal characterizing a closed clutch if the sensor detects activation of the clutch lasting for longer than a predetermined minimum period and an absolute value of the difference in the rotational speed drops below a predetermined threshold value.

12 . The control unit according to claim 11 , wherein said controller is further programmed to generate another signal characterizing an open clutch if the sensor detects activation of the clutch and a predetermined delay time has passed since detection,

13 . The control unit according to claim 12 , wherein said controller is further programmed to set the predetermined minimum period to be longer than the predetermined delay time.

14 . The control unit according to claim 9 , wherein said controller is further programmed to generate a further signal characterizing an open clutch if the difference in the rotational speed across the clutch exceeds a predetermined threshold value.

15 . The control unit according to claim 9 , wherein said controller is further programmed to:

sense a rotational speed of the internal combustion engine as a first rotational speed;

sense a rotational speed of a transmission input shaft as a second rotational speed; and

determine the difference in the rotational speed across the clutch as a difference between the first rotational speed and the second rotational speed.

16 . The control unit according to claim 9 , wherein said controller is further programmed to:

sense a rotational speed of the internal combustion engine as a first rotational speed;

sense a further rotational speed in the drive train at an output end of the change speed transmission;

determine a rotational speed of the transmission input shaft as a second rotational speed from the further rotational speed and a transmission ratio; and

determine the difference in the rotational speed across the clutch from a difference between the first rotational speed and the second rotational speed.